1. Field of the Invention
The present invention relates to a clamp device for an optical disc, and more particularly to a clamp device for an optical disc which enables a holder chuck and a plate chuck to be moved up and down to interrupt transmission of external shocks.
2. Description of the Prior Art
In general, an optical writing and reading apparatus comprises a turntable on which an optical disc is seated, means for driving the turntable, a clamp device for preventing an optical disc from being deviated from the turntable during rotation of the turntable, an optical pickup device for writing and/or reading information to and/or from an optical disc while radially moving on the optical disc, and means for driving the optical pickup device to move radially.
FIG. 1 shows an optical disc seated on a turntable, in which the optical disc is clamped by an internal clamp device.
As shown in the drawing, a driving motor 3 is fixedly attached to a deck 1, and a turntable 5 is rotatably joined to a shaft 3a of the driving motor 3.
The turntable 5 is provided at its upper surface with a center ring 7, which enables an optical disc “D” to be positioned at the center of the turntable 5. The center ring 7 is centrally formed at its upper surface with a center hole 7a of a certain depth.
When an optical disc “D” is fitted on the center ring 7 and is seated on the turntable 5, the optical disc “D” is clamped by the internal clamp device 10 to prevent the optical disc “D” from being separated form the turntable 5 during rotation of the turntable.
The internal clamp device 10 is configured such that a cover frame 12 is provided at its bottom surface with a holder chuck 14, and the holder chuck 14 is centrally formed at its lower surface with a center protrusion 14a, which is projected downward and is fitted into the center hole 7a of the center ring 7.
In addition, the holder chuck 14 is provided at its lower surface with a plate chuck 16, which is seated on an optical disc “D”.
In an operation of the internal clamp device 10, the center protrusion 14a of the holder chuck 14 is inserted into the center hole 7a to center an optical disc “D” on the turntable, and the plate chuck 16 is seated on an upper surface to prevent deviation of an optical disc “D” during rotation of the turntable 5 and to prevent a fluctuation of an optical disc “D”.
However, such a conventional internal clamp device 10 has disadvantages in that since the holder chuck 14 and the plate chuck 16 are fixedly coupled to the cover frame 12, when the internal clamp device is subjected to external shocks by a user's fault in the course of transportation or dropping of the device, the shocks are directly transmitted to the turntable 5 and the driving motor 3, thereby affecting a skew of the driving motor 3, resulting in reduction of a performance in reading data from an optical disc.
Referring to FIG. 2, there is shown an external clamp device by which an optical disc is clamped.
As shown in the drawing, the external clamp device 20 is different from the above-described internal clamp device in that a plate chuck 26 which is fixedly coupled to a lower surface of the cover frame 22 by a holder chuck 24 is externally fitted to an outer surface of a center ring 9 of a turntable 5 to position an optical disc “D” at the center of the turntable 5.
In other words, the center ring 9 is provided with a tapered outer surface, and the plate chuck 26 is centrally provided with a center-positioning concave recess 26a having a tapered inner surface corresponding to the tapered outer surface of the center ring 9.
However, such a conventional external clamp device 20 also has a disadvantage like the above internal clamp device in that the device is decreased in a performance in reading data from an optical disc owing to external shocks.